The present invention is directed generally to a counterweight door structure and more particularly to a large swinging door pivotal about an axis adjacent the upper edge thereof and having reinforced upwardly extended arms carrying counterweights in spaced relation from the top of the door.
Large doors which are supported for pivotal movement about a horizontal axis are known for airplane hangars and the like, as described in U.S. Pat. No. 2,863,181. The pivot axis for such doors, however, was situated in spaced relation below the top of the door opening to provide swinging clearance for the counterweight situated along the upper edge of the door. Thus full utilization of the door opening area was not available.
In modern airplane hangars and storage buildings for agricultural and construction equipment, it is helpful to provide a door opening of a size which occupies substantially an entire side or end of the building. It is furthermore desirable to provide a door which is movable from a closed position wherein it covers the door opening to an open position wherein the entire door opening is substantially unobstructed. For very larges doors, materials required for structural integrity by conventional construction would generally result in a door which is too heavy or expensive for practical applications.
Accordingly, it is a primary object of the invention to provide an improved counterweight door structure.
Another object is to provide a counterweight door structure having counterweights supported on upwardly extended arms at positions spaced above the top edge of the door.
Another object is to provide an improved counterweight door structure having a forwardly extended truss or reinforcement system for the counterweight support arms.
Another object is to provide an improved counterweight door structure wherein the counterweights are situated a substantial distance from the pivot axis of the door for increased leverage.
Another object is to provide an improved counterweight door structure wherein the upwardly extended counterweight support arms are spaced-apart by a distance greater than the width of the building so as to provide swinging clearance for the counterweights when the door is pivoted upwardly at least 90.degree..
Another object is to provide a counterweight door structure which is simple in construction, economical to manufacture, easy to install and efficient in operation.